Help Erlang-X Calculator
This calculator is an extension to the Erlang-C calculator. In this help function you will find all the information necessary to use this calculator. If you want to get a (better) understanding what the calculator does and how to interpret the results, please read Call center mathematics by Ger Koole. This calculator will allow you to gain a better understanding about the quantitative aspects of call centers, without knowing the mathematics themselves.
Input
In order to calculate the desired values by you, there are some specific input values required. These can be assigned by the checkbox in the first column, so here you will select which input you will provide.
Besides this input column, there is also an output column and an 'ignore'-column. In the later column you can say which aspects the calculator should ignore. So if no abandonment should be taken into consideration, you should select the 'ignore'-boxes dealing with abandonment ('average time until abandonment' and the abandonment percentage as well). See below for a detailed description on abandonment and how to cope with it.
The output column (in the middle) is intuitively clear; the value is unknown to you while you want to know it.
Required Input
In order to perform the right calculations, the calculator needs some input. This can be done by selecting at least the first three input values or by selecting just two of them. If you choose to select just two, the calculator will need some more information as well. This should be at least one of the following options:
- the average waiting time,
- the service level,
- the time untill abandonment including the abandonment percentage or
- the number of lines including the blocking percentage.
Blocking
Because the number of lines available to connect to the call center is limited, there can be some bound to the number of queued customers (= number of lines - number of agents). You can select this blocking-option by selecting the 'number of lines' or the blocking percentage as in- or output. So if you ignore both, blocking will not be taken into consideration.
Abandonment
Most callers abandon after passing some time in the queue. In order to improve the model in the way that it represents reality better, you can say abandonments can occur by selecting 'average time until abandonment' or the abandonment percentage (as in- or output). In which the first number is the average time the customers accept to spend in the queue (when their patience is over) and the latter will be a percentage of callers who abandon (who leave the queue by hanging up).
Definitions
There are different ways to define the average waiting time and the service level in the presence of abandonments and a finite number of lines. We made the following choices:
- The average waiting time and the service level are computed for all customers who will get into the queue, not those who get blocked;
- The average waiting time and the service level are computed for customers with infinite patience.
We are aware of the fact that other definitions are used in practice, see the Call Center Mathematics for a motivation of this choice.